Arc chute for air circuit breaker



Jan. 3, 1967 G. J. MEINDl-:Rs 3,295,492

ARC CHUTE FOR AIR CIRCUIT BREAKER Filed Deo. 25, 1964 2 Sheets-sheet 1 Jan. 3, 1967 G. J. MEINDERS ARC CHUTE FOR AIR CIRCUIT BREAKER 2 Sheets-Sheet 2 Filed Dec. 23, 1964 lll ff J5 f f f f f United States Patent i 3,296,402 ARC CHUTE FOR AIR CIRCUIT BREAKER Gerardus J. Meinders, Walpole, Mass., assignor to Allis- Chalmers Manufacturing Company, Milwaukee, Wis. Filed Dec. 23, 1964, Ser. No. 420,745 7 Claims. (Cl. 20G-144) This invention relates generally to arc chutes for electric circuit breakers and, particularly, to those which employ a plurality of spaced apart metal plates to divide up an are into smaller segments during extinguishment.

Some circuit breakers for interrupting alternating current use an arc chute which comprises a stack of spaced apart metal plates located between a pair of arc runners and adjacent the circuit breaker contacts. Such arc chutes operate on the principle of dividing the long arc across the runners into a multiplicity of series connected smaller arcs as it moves through the arc chute; the object being to raise the reignition voltage of the arc to a level which permanently exceeds the recovery voltage. Extinguishment is aided by the cooling of the small arcs in contact with the metal plates and by the turbulence present as the arcs move through the slots between the metal plates.

To prevent the arc from reigniting after passing through the stack of plates, it has been the practice to place insulating plates in coplanar edgewise relationship with the top edge of some or -all of the lmetal plates. However, in order for this alone to be completely effective 'there must be a close tolerance t between the edges of the metal plates and the insulating plates. Insulating plates have also been interspersed between the metal plates to aid arc extinguis'hrnent by providing .a more tortuous path for the arc, In any event, the use of insulating plates in various -arrangements ywith metal plates to aid in arc extinguishrnent, while achieving the desired electrical result, has resulted in more costly and complicated arc chutes. It is desirable, therefore, to provide new and improved -arc chutes wherein the metal plates and insulating plates are arranged so as to improve the extinguishing ability of the arc chute while at the same time reducing the number of parts otherwise required and simplifying manufacturing oper-ations.

The present invention contemplates an arc chute wherein a stack or plurality 4of spaced apart metal plates are disposed between a pair of arc runners and wherein after the arc has moved through the stack, flashover or reignition of the arc is likely to occur. In accordance with the present invention it is proposed to insert insulating plates between metal plates in a new arrangement to prevent flashover and to increase the length of the arc path but to use insulating plates in conjunction with the rest of the stack only insofar as necessary in order that as many metal plates as possible can be retained in the stack to give the voltage drop necessary to provide higher arc voltage. Arc chutes constructed in accordance Iwith the present invention have been tested and have given unexpectedly superior result-s in arc extinguishing as compared to more costly and `complicated arc chutes.

It is an object of the present invention to provide an improved arc chute which employs a combination of metal plates land insulating plates to effe-ct arc extinguishment and prevent Irestriking of the arc.

Another object is to provide an arc chute of the `afor said character which provides an elongated path for the ICC said character which is economical to fabricate and reliable in use.

Other objects and advantages will hereinafter appear.

The accompanying drawings illustrate several preferred embodiments of the invention but it is to be understood that the embodiments illustrated are susceptible of modifications with respect to details thereof without departing from the scope of the appended claims.

In the :drawings:

FIG. l is a side elevational view, partly in section, of a portion of a circuit breaker employing an arc chute incorporating the present invention;

FIG. 2 is a view taken along line II-II of FIG. 1;

FIG. 3 is a view similar to that in FIG. l but showing a second embodiment of the invention; and

FIG. 4 is a view taken along line IV--IV of FIG. 3.

Referring now to FIGS. l annd 2 of the drawings, the numerals 10 and 12 designate a stationary and movable contact, respectively, of an electric circuit breaker which separate to establish an are. An arc chute 14 is associated with contacts 10 and 12. Arc chute 14 comprises a pair of spaced apart side walls 16 and 18 which are made of electrical insulating material such as ceramic, liber, or the like. It is to be understood that the side walls 16 and 18 are mirror images of each other and are formed with suitable projections and recesses to support various components therein when the side walls are fastened together. The side walls 16 and 18 define an arcing chamber 20 in the lower portion of arc chute 14 wherein stationary -contact 10 and movable contact 12 are disposed. Stationary contact 10 is rigidly Imounted with respect to arc chute 14 and is located at one end of chamber 20. Stationary contact 10 is electrically connected to a first stationary electrically conductive `arc runner 22 which is also located at the aforesaid one end of chamber Ztl of arc chute 14. Movable contact 12 is pivotally mounted for clockwise and counterclockwise movement (with respect to FIG. l) within chamber 20 of arc chute 14 into and out of engagement, respectively, with stationary contact 10. When movable contact 12 is moved counterclockwise it comes into proximity with a second stationary electrically conductive arc runner 24 which is located at the other end of chamber 2.0` of arc chute 14 and spaced apart from arc runner 22. During circuit interruption, an arc established between the contacts 10 and 12 is transferred therefrom so that it becomes established between the arc runners 22 and 24 and travels upward thereon, as hereinafter explained.

Arc chute 14 comprises a stack of metal plates 26 which span the side walls 16 and 18 above chamber 20 and are disposed in spaced apart relationship between the arc runners 22 and 24. One end of the stack of metal plates 26 is closer to the ycontacts than the other end.

All plates 26 are of the same shape and size and may be assumed to be made of copper plated steel. The plates 26 are arranged with respect to each other so that the upper edge of each plate or the edge most remote from the contacts terminates in a rst common horizontal plane. The upper edges of the arc runners 22 and 24 also `terminate in or below the first plane. The lower edge of each plate 26 or the edge facing the contacts terminates in a second common horizontal plane. The plates 26 are held in position by entrapment in grooves 30 provided in the side walls 16 and 18. Each plate 26 is provided with a triangular slot 28 at its lower edge to guide the arc into the stack of plates during operation.

In accordance with the invention, a lirst insulating plate 32, is located between arc runner 22 and the metal plate 26 nearest to arc runner 22. Insulating plate 32 which is understood to be made of ber type insulating material, is arranged so as Ito be in overlapping relationship with a substantial part of the uppermost portion of its associated metal plate 26. Insulating plate 32 has a lower edge 34 which terminates in the aforementioned second horizontal plane in which the lower edge of each plate 26 terminates. The lower edge of insulating plate 3'2 is provided with a triangular or 'V-shaped slot 29 having an apex which lies above the apex of slot 28 in its associated metal plates 26. The upper portion of insulating plate 32 extends well above the aforementioned first plane in which the top edges of the metal plates 26 lie. Y

A second insulating plate 35, similar in size, shape and insulating properties to insulating plate 32, is located between a pair of metal plates 26 in overlapping relationship with each of the two adjacent metal plates and extends well above their upper edges. In the embodiment shown, there are three metal plates 26 intervening between the insulating plates 32 and 35. Arc chute 14 further comprises three more insulating plates 36, 37 and 38 identical in shape to the insulating plates 32 and 35 hereinbefore described. Insulating plate 36 is spaced apart from insulating plate 35 by three metal plates 26. Insulating plate 37 is spaced apart from insulating plate 36 by three metal plates 26. Insulating plate 38 is spaced apart from insulating plate 37 by two metal plates 26 and is located between arc runner 24 and the last plate 26 in the stack. The spacing between each metal plate 26 and an adjacent metal plate 26 or insulating plate is regular and is the same as the spacing between the arc runners 22 and 24 and the insulating plates 32 and 38, respectively. In effect, the metal plates 26 in the stack are arranged in groups with a plurality of metal plates in each group and each group is separated by an insulating plate, as described.

Since the slots 29 in the insulating plates 32, 35, 36, 37 and 38 are deeper than the slots 28 in the bottom edge of the plates 26, an arc can enter the stack and become established therein as a series of smaller arcs before it hits the bottom edge of any insulating plate. Furthermore, since the insulating plates 32, 35, 36, 37 and 38 transect the plane in which the top edges of the metall plates 26 lie and extend for a substantial distance on either side of this plane, flash-over of the arc at this end of the stack is effectively prevented. The arrangement of insulating plates 32, 35, 36, 37 and 38 also requires a more tortuous path for the arc as it meets the lower edges of those plates and begins to move up the stack.

Arc chute 14 is provided with means for cooling the exhaust gases expelled from the top of the stack of plates 26. Such means take the form of hollow baffle members 42 which are supported by perforated insulating members 44.

FIGS. 3 and 4 show another embodiment of the invention. An arc chute 46 shown in FIGS. 3 and 4 is similar to the arc chute 14 hereinbefore described except that it is provided with a plurality of insulating plates 48 which are disposed in edgewise association with the remote edges `of every metal plate 26 in arc chute 46. The modification disclosed in FIGS. 3 and 4 enables arc chute 46 to interrupt more powerful arcs than arc chute 14.

The insulating plates 48 are disposed in edgewise association with the remote edges of the metal plates 26 to further inhibit flashover of the arc but need not be in close tolerance fit with their associated metal plates because the ashover tendency is substantially reduced by the insulating plates 32, 35, 36,37 and 38.

Arc chute 14 operates as follows: Assume that the contacts and 12 of the circuit breaker are lclosed and that current is flowing therethrough. As movable contact 12 is moved counterclockwise (with respect to FIG. l) from closed toward open position, an arc appears between contacts 10 and 12. Because of electromagnetic vforces present, the terminal point of the arc on contact 10 then transfers to arc runner 22 and the terminal point of the arc on contact 12 moves to the extreme tip of contact 12 and the arc forms an inverted U-shape with its highest point entering within the slots 28 in those metal plates 26 at the end of the stack nearest arc runner 22. As movable contact 12 moves closer to arc runner 24, the arc terminal on the former transfers to the latter, and an 4elongated arc is established between the arc runners 22 and 24. As the elongated arc moves up through and past the slots 28 in the stack of metal plates 26, it is divided into a plurality of small arcs which are in series with each other. The small arcs tend to move upward through the stack at a relatively uniform rate. However, as the small arc between the plates 26 on either side of the insulating plates 35, 36 and 37 hits the edge of slot 29 thereof, its upward travel is slowed down. The same effect occurs as the small arcs between arc runners 22 and 24 and the plate 26 on the opposite side of the insulating plates 32 and 38, respectively, hit the edges of the slots therein. This slowing down of the arc at several points has the effect of elongating the arc and increasing its voltage. As the arc moves further through the stack it is prevented from flashing over the top edges of the metal plates 26 in the stack by the insulating plates 32, 35, 36, 37 and 38. In the embodiments shown, the arcing forces and arc by-produ-cts are mo-st numerous at the end of the arc chute nearest stationary contact 10 (i.e., the point of arc initiation) and the insulating plates disposed in this region have proven to be most effective. Since the arcing forces and by-products are less effective at the opposite end of the stack, the insulating plates thereat are sufficient to reduce the likelihood of flashover across the top of the metal plates. As previously mentioned, it is desirable to retain as many metal plates as possible in the stack in order to increase the arc voltage. Exhaust products from the arc are Acooled and condensed by means of the baffles 42 before being expelled from the arc chute.

Arc chute 46 shown in FIGS. 3 and 4 operates in the same manner as arc chute 14 but, since it is intended to handle a more powerful arc, it is provided with the insulating plates 48 which effectively aid the longer insulating plates in preventing liashover.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In combination, a pair of contacts between which an arc is established upon separation, a pair of spaced apart arc runners to which said arc is transferred from said contacts, a stack of spaced apart metal plates located between said pair of arc runners, the edge of each metal plate facing said contacts being provided with a slot, and a plurality of insulating plates arranged with respect to said metal plates so that there is an insulating plate between each end of said stack and the associated arc runner and between groups of metal plates, each insulating plate being in overlapping relationship with the uppermost por-tion of an adjacent metal plate and extending beyond the edge of each metal plate remote from said contacts, the edge of each insulating plate facing said contacts being provided with a slot which extends deeper into the insulating plate than the slot in the metal plates.

2. In combination, a pair of contacts between which an arc is established upon separation, a pair of spaced apart arc runners to which said arc is transferred from said contacts, a stack of spaced apar-t metal plates located between said pair or arc runners, the edges of said metal plates facing said contacts terminating in a rst common plane and the edges of -said metal plates remote from said contacts `terminating in a second common plane, each metal plate being provided with a slot in the edge facing said contacts, and a plurality of insulating plates arranged with respect to said metal plates so that there is an insulating plate between each end of said stack and the associated arc runner and between groups of metal plates, each insulating plate being in overlapping relationship with the uppermost portion of an adjacent metal plate and extending beyond said second common plane, the edge of r? d) each insulating plate facing said contacts terminating in said second common plane and being provided with a slot which extends deeper into the insulating plate than the slots inthe metal plates.

3. The combination according to claim 2 wherein the slots in said metal plates and said insulating plates are V-shaped.

4. The combination according to claim 3 wherein the edge of at least one of said arc runners remote from said contacts terminates in said rst common plane.

5. In combination, a pair of contacts between which an arc is established upon separation, a pair of spaced apart arc runners to which said arc is transferred from said contacts, a stack of metal plates located between said pair of arc runners, the edge of each metal plate and the edge of each arc runner remote from said contacts terminating in a iirst common plane, the edge of each metal pla-te facing said contacts terminating in a second common plane and being provided with a slot, said metal plates being divided into a plurality of spaced apart groups with a plurality of metal plates in each group, the plates in each group spaced apart a predetermined distance from each other and the groups being spaced apart twice said predetermined distance from each other and from the arc runners, and a plurality of insulating plates arranged with respect to said metal plates so Ilthat there is an insulating plate between each end of said stack and the associated arc runner and between said groups, the edge of each insulating plate remote from said contacts terminating beyond said rst common plane, the edge of each insulating plate facing said contacts terminating in said second common plane and being provided with a slot which extends deeper into the insulating plate than the slots in the metal plates.

6. The combination according to claim 5 wherein the slots in said metal plates and said insulating plates are V-shaped.

7. The combination according to clairn 5 including another plurality of insulating plates and wherein each insulating plate in said other plurality is in edgewise association with the remote edge of a single metal plate.

References Cited by the Examiner UNTED STATES PATENTS 2,215,797 9/1940 Sauer 200-147 2,734,970 2/1956 Spears 200-147 2,908,787 10/1959 Scully 200-144 3,031,552 4/1962 Stewart 200-144 ROBERT K. SCHAEFER, Primary Examiner. R. S. MACON, Assistant Examiner. 

1. IN COMBINATION, A PAIR OF CONTACTS BETWEEN WHICH AN ARC IS ESTABLISHED UPON SEPARATION, A PAIR OF SPACED APART ARC RUNNERS TO WHICH SAID ARC IS TRANSFERRED FROM SAID CONTACTS, A STACK OF SPACED APART METAL PLATES LOCATED BETWEEN SAID PAIR OF ARC RUNNERS, THE EDGE OF EACH METAL PLATE FACING SAID CONTACTS BEING PROVIDED WITH A SLOT, AND A PLURALITY OF INSULATING PLATES ARRANGED WITH RESPECT TO SAID METAL PLATES SO THAT THERE IS AN INSULATING PLATE BETWEEN EACH END OF SAID STACK AND THE ASSOCIATED ARC RUNNER AND BETWEEN GROUPS OF METAL PLATES, EACH INSULATING PLATE BEING IN OVERLAPPING RELATIONSHIP WITH THE UPPERMOST PORTION OF AN ADJACENT METAL PLATE AND EXTENDING BEYOND THE EDGE OF EACH METAL PLATE REMORE FROM SAID CONTACTS, THE EDGE OF EACH INSULATING PLATE FACING SAID CONTACTS BEING PROVIDED WITH A SLOT WHICH EXTENDS DEEPER INTO THE INSULATING PLATE THAN THE SLOT IN THE METAL PLATES. 